JP2004208221A - High frequency band filtering apparatus and portable information terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency band filtering apparatus and a portable information terminal which are miniaturized and have wide passbands. <P>SOLUTION: A high frequency filtering apparatus 51 to be used for a specific communication band from 1 to 10GHz is provided with a plurality of parallel disposed piezoelectric thin film resonator type filters 11, 12, 13, 14 which have different passbands respectively and of which the entire passbands are selected to cover the specific communication band, and low noise amplifiers which are independently and directly connected to the output side of the piezoelectric thin film resonator type filters 11, 12, 13, 14. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a portable information terminal, and more particularly, to a high-frequency band filter device used in a microwave range of 0.8 to 10 GHz and a portable information terminal including the high-frequency band filter device.
[0002]
[Prior art]
2. Description of the Related Art In recent years, wireless communication technology has been remarkably developed, and development for high-speed transmission of information is being advanced. With the introduction of the PHS system, the third-generation mobile communication, the wireless LAN, and the like, the frequency band used in the wireless communication technology uses a frequency band of about 2 GHz, and the number of subscribers, the number of terminals, and the like are increasing dramatically. The frequency of the carrier has been further increased, and commercialization of the wireless LAN system in the 5 GHz band has also started.
[0003]
High-frequency communication devices using such wireless communication technology are required to be reduced in size and weight. In particular, when a high-frequency communication device is used for a portable information terminal, the RF front-end unit that processes a high-frequency (RF) signal performs filtering using the pass band characteristics of a cavity resonator or an LC circuit, so that the size of the device is small. There is a limit to the reduction in thickness and thickness.
[0004]
Therefore, as one of means for reducing the size of a high-frequency communication device, “Film Bulk Acoustic Resonator (FBAR)” has attracted attention (for example, see Patent Documents 1 and 2). The “thin film type bulk acoustic wave resonator” includes a lower electrode in contact with the air layer, a piezoelectric thin film in contact with the lower electrode, and an upper electrode in contact with the upper portion of the piezoelectric thin film. The wave is propagated to obtain resonance at the frequency of the elastic bulk wave. Since this thin film type bulk acoustic wave resonator can be formed with a resonator structure on a semiconductor substrate, it is easy to reduce the size and easily realize a size of 1 mm or less, which is difficult with existing filters. Further, mounting on a transistor, an IC, or an LSI is easy. If an aluminum nitride (AlN) thin film is used as the piezoelectric thin film, a filter having a pass band Δf of about 200 MHz as shown in FIG. 14 can be manufactured.
[0005]
[Patent Document 1]
JP 2001-24476 A
[0006]
[Patent Document 2]
JP-A-2000-30594
[0007]
[Problems to be solved by the invention]
Consider the 5 GHz communication band described above. The passband currently available in Japan is 5.15 to 5.25 GHz. In Europe, the 5.15 to 5.35 GHz band and the 5.47 to 5.725 GHz band can be used, and in the United States, the 5.725 to 5.825 GHz band can be used. As described above, the communication band usable in various countries around the world even at 5 GHz is dispersed over a wide area. However, the above-mentioned filter using the thin film type elastic bulk acoustic wave resonator has a disadvantage that it cannot cope with all communication bands in various countries of the world because its pass band is as narrow as 200 MHz at most. Therefore, as shown in FIG. 13, attempts have been made to obtain a high-bandwidth band-pass filter by connecting a plurality of filters 100 and 101 using a thin film type elastic bulk acoustic wave resonator in parallel. However, even if a plurality of filters 100 and 101 using a thin film type bulk acoustic wave resonator are coupled in parallel, there is a problem that desired pass band characteristics cannot be obtained because the phase characteristics of the filters interfere with each other.
[0008]
SUMMARY OF THE INVENTION The present invention has been made to eliminate the above-mentioned disadvantages of the prior art, and has as its object to provide a compact high-frequency band filter device having a wide pass band and a portable device including the high-frequency band filter device. It aims to provide a type information terminal.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a first feature of the present invention is a high frequency band filter device used for a specific communication band in 0.8 to 10 GHz, each having a different pass band from each other. A plurality of piezoelectric thin-film resonator-type filters that are selected so as to cover a specific communication band as a whole and are arranged in parallel, and a low-noise amplifier that is directly connected to the output side of the piezoelectric thin-film resonator-type filters independently and directly The gist is a high-frequency band filter device comprising: According to the first feature of the present invention, in a communication band of 0.8 to 10 GHz, a plurality of piezoelectric thin-film resonator filters each having a pass band different from each other and arranged in parallel, for example, 5 GHz Since the pass band is selected so as to cover the whole of a specific communication band such as a band, a small-sized high-frequency band filter device having a wide pass band can be obtained. Further, since the low-noise amplifiers are directly and independently connected to the output side of the piezoelectric thin-film resonator type filter independently, it is possible to provide a high-frequency band filter device in which deterioration of a high-frequency signal is reduced.
[0010]
A second feature of the present invention is that a plurality of piezoelectric thin-film resonator filters selected so that their pass bands are different from each other, and a low-noise amplifier directly and independently connected to the output side of the piezoelectric thin-film resonator filters, respectively. A high-frequency front-end unit having an intermediate frequency processing unit connected to the high-frequency front end unit, and a baseband processing unit connected to the intermediate frequency processing unit, and a specific communication band in the 0.8 to 10 GHz band. The gist is that the terminal is a portable information terminal that performs communication. According to the second feature of the present invention, the high-frequency front end unit has a pass band different from each other within a communication band of 0.8 to 10 GHz and covers a specific communication band as a whole. Are arranged. On the output side of the piezoelectric thin film resonator type filter, low noise amplifiers are directly and independently connected in series. Therefore, it is possible to provide a small-sized portable information terminal having a wide pass band in a high frequency range of 0.8 to 10 GHz band, little signal degradation, and excellent in pass characteristics.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, first to third embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the average dimension, the ratio of the thickness of each layer, and the like are different from actual ones. In addition, it is needless to say that the drawings include portions having different dimensional relationships and ratios.
[0012]
The first to third embodiments described below exemplify an apparatus and a method for embodying the technical idea of the present invention. The shape, structure, arrangement and the like are not specified as follows. The technical concept of the present invention can be variously modified within the scope of the claims.
[0013]
(Portable information terminals)
Before describing the high frequency band filter devices according to the first to third embodiments of the present invention, a 0.8 to 10 GHz band superheterodyne radio suitable for using these high frequency band filter devices is described. An example of the overall configuration of the portable information terminal 1 that performs signal transmission and reception will be described. Here, the portable information terminal 1 in the 5 GHz band will be described as an example.
[0014]
For example, as shown in FIG. 1, the portable information terminal 1 includes a high-frequency front-end unit (RF front-end unit) 2, an intermediate frequency processing unit (IF unit) 3 connected to the RF front-end unit 2, A baseband processing unit (BB unit) 4 connected to the processing unit 3;
[0015]
The RF front-end unit 2 includes a high-frequency band filter device 51, a mixer 53 connected to the high-frequency band filter device 51, a local oscillator 52 connected to the mixer 53, and a high-frequency band filter device 51, which will be described in detail in the following first to third embodiments. An amplifier 54 is provided. The mixer 53 mixes the RF signal output from the high-frequency band filter device 51 and the RF signal output from the local oscillator 52, and generates an intermediate frequency (IF) signal of, for example, about 200 MHz to 500 MHz. The high-frequency band filter device 51 further includes antennas 75 and 76 that supply an RF signal to the high-frequency band filter device 51. In FIG. 1, two antennas 75 and 76 are connected, but this is an example, and the number of antennas is limited to two as described in detail in the first to third embodiments. Not done. The RF signals received by the antennas 75 and 76 mixed by the mixer 53 and the RF signal output from the local oscillator 52 are transmitted to the intermediate frequency (IF) processing unit 3 via the amplifier 54.
[0016]
The intermediate frequency processing unit 3 includes an intermediate frequency (IF) filter 56, an automatic gain control (AGC) circuit 55 connected to the IF filter 56, an I / Q demodulation circuit 57 connected to the automatic gain control (AGC) circuit 55, An IF local oscillation circuit 58 connected to the I / Q demodulation circuit 57 is provided. The IF filter 56 extracts the difference frequency between the RF signals received by the antennas 75 and 76 and the RF signal output from the local oscillator 52, and the automatic gain control (AGC) circuit 55 converts the IF signal, which is the difference frequency, into an IF signal. Be stabilized. This IF signal is subjected to quadrature phase modulation by the I / Q demodulation circuit 57, and an I signal and a Q signal having phases shifted by 90 ° from each other are generated. In the mixer 85 and the mixer 86 included in the I / Q demodulation circuit 57, the signals of the IF local oscillation circuit 58 are mixed, and a baseband I signal and a baseband Q signal of a low frequency, for example, 10 MHz or less are generated. The baseband I signal and the baseband Q signal having different phases by 90 ° are transmitted to the baseband processing unit (BB unit) 4, respectively.
[0017]
The baseband processing unit 4 includes baseband filters 81 and 82, A / D converters 83 and 84, and a digital baseband processor (DBBP) 85. The baseband I signal and the baseband Q signal extracted through the baseband filter 81 and the baseband filter 82 are respectively converted into a digital baseband I signal and a baseband Q signal by an AD converter 83 and an AD converter 84. The signal is processed by a digital baseband processor (DBBP) 85.
[0018]
FIG. 1 shows only the RF front-end unit 2 on the receiving side, the intermediate frequency processing unit 3 on the receiving side, and the baseband processing unit 4 on the receiving side for convenience. Of course, there is an RF front-end section on the side, an intermediate frequency processing section on the transmitting side, and a baseband processing section on the transmitting side. The RF front end on the transmitting side (not shown) is provided with a power amplifier module including microwave power transistors connected in multiple stages. As the microwave power transistor, a high-frequency active element such as a heterojunction bipolar transistor (HBT) and a high electron mobility transistor (HEMT) is used. The high-frequency active device may be a gallium arsenide-based compound semiconductor device or a Si-based compound semiconductor device such as SiGe. Further, an element such as a MOSFET using Si may be used. The transmission-side intermediate frequency processing unit (not shown) includes an I / Q modulation circuit having a configuration similar to that of the I / Q demodulation circuit 57 of the reception-side intermediate frequency processing unit 3. The baseband processing unit on the transmitting side (not shown) is provided with a DA converter for converting a digital baseband I signal and a baseband Q signal from a digital baseband processor (DBBP) into an analog signal. . The digital baseband processor (DBBP) 85 may be a device common to the baseband processing unit on the transmitting side and the baseband processing unit 4 on the receiving side. Although not shown, when the antennas 75 and 76 are shared between the transmission side and the reception side, a switch circuit for switching between transmission and reception is provided.
[0019]
Hereinafter, the high-frequency band filter device 51 applicable to the 5 GHz band in the first to third embodiments will be described.
[0020]
(First Embodiment)
As shown in FIG. 2, the high-frequency band filter device 51 according to the first embodiment of the present invention has different pass bands in the communication band of 5 GHz, and the entire pass band covers the communication band of 5 GHz. (Fourth to fourth piezoelectric thin film resonator type filters) 11, 12, 13, and 14 selected as described above, and first to fourth piezoelectric thin film resonator filters. Low-noise amplifiers (first to fourth low-noise amplifiers) 21, 22, 23, and 24 are directly and independently connected to the output sides of the slave filters 11, 12, 13, and 14, respectively. Although not shown in FIG. 2, a mixer 53 as shown in FIG. 1 is further connected to the first to fourth low-noise amplifiers 21, 22, 23, and 24 on the output side. Mixed with the output signal. A switch circuit 6 connected to an antenna 7 is connected to the input side of the piezoelectric thin-film resonator type filters 11, 12, 13, and 14.
[0021]
The first to fourth piezoelectric thin film resonator type filters 11, 12, 13, 14 are arranged in parallel with each other, as shown in FIG. For example, the first piezoelectric thin film resonator type filter 11 is 4.90 to 5.00 GHz, the second piezoelectric thin film resonator type filter 12 is 5.03 to 5.09 GHz, and the third piezoelectric thin film resonator type filter 13 Is adjusted to 5.15 to 5.35 GHz, and the fourth piezoelectric thin film resonator type filter 14 is adjusted to 5.725 to 5.825 GHz, respectively, and covers a communication band of 5 GHz band in various countries in the world as a whole. The first to fourth low-noise amplifiers 21, 22, 23, and 24 independently amplify the signals output from the first to fourth piezoelectric thin-film resonator filters 11, 12, 13, and 14, respectively. The first to fourth low-noise amplifiers 21, 22, 23, and 24 use high-frequency active elements such as HBTs and HEMTs. The high-frequency active device may be a gallium arsenide-based compound semiconductor device or a Si-based compound semiconductor device such as SiGe. Further, an element such as a MOSFET using Si may be used. The switch circuit 6 receives the selection signal SEL output from the control terminal 5 of the baseband processing unit 4 shown in FIG. 1 and selects one of the first to fourth piezoelectric thin-film resonator filters 11, 12, 13, and 14. Or choose. The switch circuit 6 is a semiconductor switch including active elements such as four field effect transistors (FETs). That is, the selection signal SEL is input to one of the control electrodes of the four active elements, and one of the piezoelectric thin film resonator type filters 11, 12, 13, and 14 is selected. A radio (RF) signal received by the antenna 7 is selected by the switch circuit 6 and sent to one of the first to fourth piezoelectric thin film resonator type filters 11, 12, 13, and 14 in the corresponding frequency band. .
[0022]
As shown in FIG. 3A and FIG. 4, the first to fourth piezoelectric thin film resonator type filters 11, 12, 13, 14 each include three thin film type elastic bulk acoustic wave resonators connected in a T-shape. (FBAR) 30a, 30b, and 30c. That is, as shown in the four-terminal circuit of FIG. ₁ Thin-film type elastic bulk acoustic wave resonator 30a whose input side is connected to a first output terminal O ₁ And a second thin film bulk acoustic wave resonator 30b whose output side is connected to ₁ Are connected in series with each other. The third thin film bulk acoustic wave resonator 30c is connected to the node p ₁ And the second input terminal I _Two Between the second output terminal and _Two Node p, which is the midpoint of the branch connecting _Two Connected between. The third thin film bulk acoustic wave resonator 30c is connected to the node p ₁ And p _Two This is equivalent to being inserted as a parallel impedance element between them. As shown in FIG. 3B, the center frequency of the series resonance by the first and second thin film bulk acoustic wave resonators 30a and 30b and the center of the parallel resonance of the third thin film bulk acoustic wave resonator 30c. The frequencies are set to be slightly different. However, the frequency of the series resonance of the first and second thin film type elastic bulk acoustic wave resonators 30a and 30b and the parallel resonance frequency of the third thin film type elastic bulk acoustic wave resonator 30c are adjusted to match. , As shown in FIG. 3 (b).
[0023]
As shown in FIG. 5, for example, the first thin film bulk acoustic wave resonator 30 a includes a silicon substrate 31, a buffer layer 32 disposed over the entire surface of the silicon substrate 31, and a portion in contact with the buffer layer 32. Then, the left end which contacts the bridge-type (cantilever-type) lower electrode 33a, the other part of the buffer layer 32, and the lower electrode 33a which are arranged with the contact portion as a fulcrum, and directly contacts the buffer layer 32 Is a bridge-type (double-supported) piezoelectric thin film 34a, which is disposed as one fixed end, and the right end located directly above the portion where the lower electrode 33a is in direct contact with the buffer layer is the other fixed end. It has a bridge-type upper electrode 35a disposed on the thin film 34a. A cavity (air gap) 36a is provided between the buffer layer 32 and the lower electrode 33a. The first thin film type elastic bulk acoustic wave resonator 30a propagates the elastic bulk acoustic wave in the thickness direction of the piezoelectric thin film 34a inserted between the lower electrode 33a and the upper electrode 35a which are in contact with the cavity 36a. The passband characteristic is obtained by the resonance frequency of the wave. The adjustment of the pass band is performed by adjusting the thickness of the lower electrode 33a, the piezoelectric thin film 34a, and the upper electrode 35a, particularly, the thickness of the piezoelectric thin film 34a. For example, when the resonator is set to a high frequency range of 0.8 to 10 GHz, the thickness of each of the lower electrode 33a, the piezoelectric thin film 34a, and the upper electrode 35a is selected to be 0.3 to 3 μm. As the lower electrode 33a and the upper electrode 35a, a metal thin film such as an aluminum (Al) film is used. The piezoelectric thin film 34a is an AlN thin film, barium titanate (TiBaO) _Three ) A thin film or a zinc oxide (ZnO) thin film is used. In particular, the AlN thin film can obtain good characteristics by controlling the orientation. In this case, it is preferable to control the orientation of the AlN thin film to an X-ray rocking curve of 2 ° or less. It is preferable that the bridge portion of the piezoelectric thin film 34a is stabilized by stress control. The buffer layer 32 is made of a silicon oxide film (SiO _Two Film), silicon nitride film (Si _Three N _Four And the like can be used. The cavity 36a is formed by patterning a sacrificial layer such as a polysilicon film on the buffer layer 32, depositing a lower electrode 33a, a piezoelectric thin film 34a, and an upper electrode 35a thereon in that order, and then removing the sacrificial layer by etching. It can be easily realized. Although not shown, the second and third thin film bulk acoustic wave resonators 30b and 30c have the same cross-sectional structure as the first thin film bulk acoustic wave resonator 30a.
[0024]
As shown in FIG. 4, the first to third thin film bulk acoustic wave resonators 30a, 30b, 30c are monolithically integrated on a silicon substrate 31. A 5 GHz band coplanar transmission line is formed by the input-side signal wiring 302 and the ground plates 33c and 33d located on both sides thereof. In the plan view shown in FIG. 4, the buffer layer 32 is exposed in the gap between the input-side signal wiring 302 and the ground plate 33c and in the gap between the input-side signal wiring 302 and the ground plate 33d. The input signal wiring 302 is connected to the lower electrode 33a of the first thin film bulk acoustic wave resonator 30a. A piezoelectric thin film 34a is disposed above the lower electrode 33a, and an upper electrode 35a is disposed above the piezoelectric thin film 34a to form a first thin film elastic bulk acoustic wave resonator 30a. The upper electrode 35a of the first thin-film type elastic bulk acoustic wave resonator 30a and the upper electrode 35c of the third thin-film type elastic bulk acoustic wave resonator 30c located at the center of FIG. Connected. The piezoelectric thin film 34c is arranged below the upper electrode 35c of the third thin film bulk acoustic wave resonator 30c, and the lower electrode 33c is arranged below the piezoelectric thin film 34c. The lower electrode 33c is integrally connected to the ground plate 33c of the coplanar transmission line. The upper electrode 35c of the third thin film bulk acoustic wave resonator 30c and the upper electrode 35b of the second thin film bulk acoustic wave resonator 30b shown at the top of FIG. It is connected. A piezoelectric thin film 34b is arranged below the upper electrode 35b of the second thin film bulk acoustic wave resonator 30b, and a lower electrode 33b is arranged below the piezoelectric thin film 34. The lower electrode 33b is connected to the output signal wiring 303. The output signal wiring 303 and the ground plates 33c and 33d form a 5 GHz band coplanar transmission line. The three thin film bulk acoustic wave resonators 30a, 30b and 30c connected in a T-shape as shown in FIGS. 3A, 4 and 5 are composed of first to fourth piezoelectric thin film resonator type filters 11. , 12, 13, and 14 respectively. Then, the first to fourth piezoelectric thin film resonator type filters 11, 12, 13, and 14 are monolithically formed on the same silicon substrate 31, and a high frequency filter chip 602 as shown in FIG. 6 is realized. Although a coplanar transmission line is shown in FIG. 4 as the high-frequency transmission line, another high-frequency transmission line such as a microstrip line may be used.
[0025]
As shown in FIG. 6, a switch circuit chip 601 equipped with a switch circuit, a high frequency filter chip 602, and a low noise amplifier chip 603 equipped with a low noise amplifier are hybridly integrated on the same ceramic substrate 41. . The switch circuit chip 601, the high frequency filter chip 602, and the low noise amplifier chip 603 are connected to signal lines (metal wires) 412 to 415 of a high frequency transmission line formed on the ceramic substrate 41 via bumps 501 to 506 and the like. Have been. Further, the switch circuit chip 601, the high frequency filter chip 602, and the low noise amplifier chip 603 are sealed with a resin 521 to form the semiconductor package 8. For example, in FIG. 6, a ground plate 411 is formed below the ceramic substrate 1. The ground plate 411, the ceramic substrate 41, and the signal lines (metal wires) 412 to 415 constitute a 5 GHz band microstrip line. However, the switch circuit 6, the first to fourth piezoelectric thin film resonator type filters 11, 12, 13, and 14, and the first to fourth low noise amplifiers 21, 22, 23 and 24 are all mounted on the same semiconductor substrate. Alternatively, it may be monolithically integrated. First to fourth piezoelectric thin film resonator type filters 11, 12, 13, 14 and first to fourth low noise amplifiers 21, 22, 23, 24 are formed on independent semiconductor chips, respectively, It may be mounted on the ceramic substrate 41 in a hybrid manner.
[0026]
As described above, according to the high-frequency band filter device 51 according to the first embodiment of the present invention, as shown in FIG. 7, the plurality of frequency regions A, B, C, and D are covered, and as a whole, It is possible to obtain a high-frequency band filter device having a wide band of about 1 GHz. Further, the first to fourth piezoelectric thin film resonator type filters 11, 12, 13, and 14 are switched by the switch circuit 6 and selectively operated, so that the first to fourth piezoelectric thin film resonator type filters 11, 12, Even when 12, 13, and 14 are arranged adjacent to each other, mutual interference between the first to fourth piezoelectric thin-film resonator filters 11, 12, 13, and 14, and signal deterioration due to the mutual interference are small.
[0027]
As shown in FIG. 6, the switch circuit 6, the first to fourth piezoelectric thin film resonator type filters 11, 12, 13, and 14, and the first to fourth low noise amplifiers 21, 22, 23, and 24 are provided. Can be mounted on the same ceramic substrate 41. Therefore, the high-frequency transmission lines routed to the first to fourth low-noise amplifiers 21, 22, 23, and 24 can be shortened, and the size of the package can be reduced. Shortening of the high-frequency transmission line can also reduce problems of local leak and signal delay.
[0028]
(Modification of First Embodiment)
As shown in FIG. 8, a high-frequency band filter device 51 according to a modification of the first embodiment of the present invention has independent output sides of first to fourth low-noise amplifiers 21, 22, 23, and 24, respectively. 2 in that it further has first to fourth matching circuits 25, 26, 27, and 28 connected in series. Others are substantially the same as the high frequency band filter device shown in FIG. The first to fourth matching circuits 25, 26, 27, and 28 have an output terminal q. ₁ 1 and is mixed with the output signal of the local oscillator 52. The matching circuits 25, 26, 27, and 28 adjust the impedance of the first to fourth piezoelectric thin-film resonator filters 11, 12, 13, and 14, and are configured by combining stubs or inductors and capacitors. What is done is used.
[0029]
According to the high frequency band filter device 51 shown in FIG. 8, the first to fourth matching circuits 25, 26, 27, 28 are independent on the output side of the first to fourth low noise amplifiers 21, 22, 23, 24. Therefore, the phases of the first to fourth piezoelectric thin film resonator type filters 11, 12, 13, and 14 can be adjusted. For this reason, a high frequency band filter device with little signal degradation can be obtained. Selection of the first to fourth piezoelectric thin-film resonator filters 11, 12, 13, and 14 is controlled by a selection signal SEL from the baseband processing unit 4, and is input to the gate of a transistor constituting the switch circuit 6, Since switching can be performed, a broadband high-frequency band filter device as shown in FIG. 7 can be obtained. Further, any one of the first to fourth piezoelectric thin film resonator type filters 11, 12, 13, 14 is selected by the switch circuit 6, so that the first to fourth piezoelectric thin film resonator type filters 11, 12 are selected. , 13, and 14 have little mutual interference. Therefore, according to the high frequency band filter device 51 according to the modification of the first embodiment of the present invention, it is possible to obtain a high frequency band filter device with little signal degradation and excellent pass band characteristics.
[0030]
(Second embodiment)
As shown in FIG. 9, a high-frequency band filter device 51 according to a second embodiment of the present invention includes a switch circuit 6 shown in FIG. 13 is different from the high frequency band filter device according to the first embodiment in that it does not have on the input side. The first to third piezoelectric thin-film resonator filters 11, 12, 13 are directly connected to the first to third antennas 71, 72, 73, respectively, independently. Others are the same as the high frequency band filter device shown in FIG.
[0031]
The first to third antennas 71, 72, and 73 receive an external RF signal and transmit the RF signal directly to each of the first to third piezoelectric thin-film resonator filters 11, 12, and 13. The RF signals output from the first to third piezoelectric thin-film resonator filters 11, 12, and 13 are input to the mixer 53 shown in FIG. 1 via the output terminal q2 and mixed with the output signal of the local oscillator 52. Is done. As the first to third antennas 71, 72, 73, small patch antennas or dielectric ceramic antennas are used.
[0032]
According to the high frequency band filter device 51 according to the second embodiment of the present invention, the first to third piezoelectric thin film resonator type filters 11, 12, 13 are provided with the first to third antennas 71, 72, 73, respectively. Since they are directly connected in a one-to-one relationship, the number of switch circuits 6 as shown in FIG. 2 can be reduced. As a result, signal loss in the switch circuit 6 can be reduced. Further, since a circuit for controlling the switch circuit 6 for selecting the type of the first to third piezoelectric thin film resonator type filters 11, 12, 13 is not required, the size can be further reduced. By employing a small patch antenna or the like as the first to third antennas 71, 72, 73, the high-frequency band filter device shown in FIG. 9 can be further miniaturized.
[0033]
Further, since the first to third piezoelectric thin film resonator type filters 11, 12, and 13 have different frequency ranges, a plurality of frequency bands A, B, and C are covered as shown in FIG. As a whole, a high-frequency band filter device having a wide band of about 1 GHz can be obtained.
[0034]
(Third embodiment)
As shown in FIG. 11, the high frequency band filter device 51 according to the third embodiment of the present invention includes a first piezoelectric thin film resonator type filter 11 as a top filter and a fifth piezoelectric thin film filter as an interstage filter. A first low-noise amplifier 21 is directly connected between the thin-film resonator type filter 15 and forms an independent first series circuit. A second low-noise amplifier 22 is directly connected between the second piezoelectric thin-film resonator type filter 12 as a top filter and the sixth piezoelectric thin-film resonator type filter 16 as an inter-stage filter, and is independent. This constitutes a second series circuit. A third low-noise amplifier 23 is directly connected between the third piezoelectric thin-film resonator type filter 13 as a top filter and the seventh piezoelectric thin-film resonator type filter 17 as an interstage filter, and is independent. This constitutes a third series circuit. The first piezoelectric thin film resonator type filter 11 and the fifth piezoelectric thin film resonator type filter 15 have the same pass band. The second piezoelectric thin film resonator type filter 12 and the sixth piezoelectric thin film resonator type filter 16 have the same pass band. The third piezoelectric thin film resonator type filter 13 and the seventh piezoelectric thin film resonator type filter 17 have the same pass band. The first, second and third piezoelectric thin film resonator type filters 11, 12, 13 are respectively arranged in parallel. Others are substantially the same as the high frequency band filter device shown in FIG.
[0035]
As shown in FIG. 11, the first to third piezoelectric thin film resonator type filters 11, 12, and 13 each have an input side connected to a switch circuit 6a, and an output side independently having first to third low noise amplifiers. 21, 22, 23 respectively. The fifth to seventh piezoelectric thin-film resonator filters 15, 16, 17 have their input sides independently connected to the first to third low-noise amplifiers 21, 22, 23, respectively, and their output sides connected to the switch circuit 6b. It is connected. The switch circuit 6b is connected to the control terminal 5 and the mixer 53. For example, in the communication band of the 5 GHz band, the first and fifth piezoelectric thin film resonator type filters 11 and 15 are 4.90 to 5.00 GHz, and the second and sixth piezoelectric thin film resonator type filters 12 and 16 are 5 .15 to 5.35 GHz, and the third and seventh piezoelectric thin film resonator type filters 13 and 17 are adjusted to 5.725 to 5.825 GHz. The adjustment of the frequencies of the first to third piezoelectric thin film resonator type filters 11 to 13 and the fifth to seventh 15 to 17 is performed as described in the first embodiment. This is performed by adjusting the thickness of the piezoelectric thin film 34, the lower electrode 33, and the upper electrode 35, particularly the thickness of the piezoelectric thin film 34. As described in the first embodiment, high-frequency active elements such as HBTs and HEMTs are used for the first to third low-noise amplifiers 21, 22, and 23. The switch circuits 6a and 6b may use semiconductor switches composed of semiconductor active elements such as FETs as in the first embodiment. For example, a piezoelectric thin film actuator element 60 as shown in FIG. 12 may be used.
[0036]
As shown in FIG. 12, the piezoelectric thin film actuator element 60 includes a silicon substrate 61, a ground plate 610 made of a metal thin film disposed on the entire surface of the silicon substrate 61, a buffer layer 62 disposed on the ground plate 610, and a buffer layer. A bridge-type (cantilever-type) lower electrode 63 that is partially in contact with the upper electrode 62 and is disposed with the contact portion (fixed end) as a fulcrum, and a bridge-type piezoelectric thin film 64a that is disposed on the lower electrode 63 , And a switch electrode 67 a that is in contact with the buffer layer 62 and is disposed immediately below the free end of the lower electrode 63. A cavity (air gap) 66 is provided between the buffer layer 62 and the lower electrode 63. The piezoelectric thin-film actuator element 60 brings the free end of the lower electrode 63 opposed to the switch electrode 67a through the air gap 66 into contact with the switch electrode 67a by a piezoelectric strain force, and makes the lower electrode 63 and the switch electrode 67a conductive. When the voltage applied between the lower electrode 63 and the switch electrode 67a is released, the piezoelectric distortion force is eliminated, and the conduction between the free end of the lower electrode 63 and the switch electrode 67a is interrupted by the elasticity of the piezoelectric thin film 64a. As the lower electrode 63 and the switch electrode 67a, a metal thin film such as an Al thin film, a Cu thin film, and an Au thin film is used. Ni plating or Au plating may be performed on the Cu thin film. As the piezoelectric thin film 64a, an AlN thin film or the like can be used. The buffer layer 62 is made of SiO _Two Film, Si _Three N _Four A membrane or the like can be used. The air gap 66 is formed by patterning a sacrificial layer such as polysilicon on the buffer layer 62 and the switch electrode 67a, depositing the lower electrode 63 and the piezoelectric thin film 64a thereon in that order, and then removing the sacrificial layer by etching. Is done. In this manner, a desired switch circuit can be configured by using the piezoelectric thin film actuator element 60 shown in FIG. 12 as a constituent unit of the switches 6a and 6b. For example, a signal line including an MIM capacitor or the like is connected to the lower electrode 63, and a thin-film microstrip line can be formed between the signal line and the ground plate 610 using the buffer layer 62 as a dielectric layer. In addition to the thin film microstrip line, another high frequency transmission line such as a coplanar transmission line may be used.
[0037]
In the high frequency band filter device 51 according to the third embodiment of the present invention, the first and fifth piezoelectric thin film resonator type filters 11 and 15 having different pass bands in the 0.8 to 10 GHz band, respectively, are provided. The operations of the second and sixth piezoelectric thin film resonator filters 12 and 16 and the third and seventh piezoelectric thin film resonator filters 13 and 17 are selectively controlled by a selection signal SEL from the control terminal 5. . Therefore, a high-frequency band filter device with little mutual interference can be obtained. Further, as shown in FIG. 12, a voltage is input to the lower electrode 63 and the switch electrode 67a constituting the switch circuit 6, and the voltage is mechanically switched, so that the high-frequency filter circuit having a plurality of frequency regions is selectively operated. Can be done. Further, in a semiconductor switch using a semiconductor active element such as an FET, conduction loss and high-frequency loss occur due to channel resistance and ohmic loss. By using the piezoelectric thin film actuator element 60 shown in FIG. 12 as a switch circuit, the loss of the RF signal can be suppressed lower than that of an FET or the like in which the loss of the RF signal increases. As described with reference to FIG. 6, the switch circuits 6a and 6b, the first and fifth piezoelectric thin film resonator type filters 11 and 15, the second and sixth piezoelectric thin film resonator type filters 12 and 16, By mounting the third and seventh piezoelectric thin-film resonator filters 13 and 17 and the low-noise amplifiers 21, 22, and 23 in the same package, they are routed to the first to third low-noise amplifiers 21, 22, and 23. High-frequency transmission lines can be shortened. Shortening of the high-frequency transmission line can also reduce problems of local leak and signal delay. If the switch electrode 67a shown in FIG. 12 is designed to ensure the isolation of the RF signal, the interference between the piezoelectric thin film resonator type filters can be further reduced.
[0038]
(Other embodiments)
As described above, the present invention has been described with reference to the first to third embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art.
[0039]
In the above-described first to third embodiments, the high-frequency band filter device of the 5 GHz band has been described. However, this is merely an example, and the high-frequency band filter device of the 1.5 GHz, 2.1 GHz, 2.5 GHz band, etc. Of course, the present invention can be applied to a high-frequency band filter device used for another communication band in the 10 to 10 GHz band.
[0040]
In the first embodiment, a switch circuit 6 may be further arranged on the output side of the first to fourth low noise amplifiers 21, 22, 23, 24.
[0041]
Of course, the configuration of the piezoelectric thin film actuator element 60 shown in the third embodiment can also be used for the switch circuits 6, 6a, 6b according to the first and second embodiments. Further, in the first embodiment, the case where an FET is used as a semiconductor switch has been described. Various transistors such as an induction transistor (SIT) and a HEMT may be used.
[0042]
Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the matters specifying the invention described in the claims appropriate from this disclosure.
[0043]
【The invention's effect】
According to the present invention, it is possible to provide a small-sized high-frequency band filter device having a wide pass band and a portable information terminal.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an example of an overall configuration of a portable information terminal according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a high-frequency band filter device according to the first embodiment of the present invention.
3A shows a filter configuration of the piezoelectric thin film resonator type filter shown in FIG. 2, and FIG. 3B shows characteristics of the piezoelectric thin film resonator type filter.
FIG. 4 is a plan view showing an example of the piezoelectric thin film resonator type filter shown in FIG.
FIG. 5 is a view showing a cross section AA of the piezoelectric thin film resonator type filter shown in FIG. 4;
FIG. 6 is a diagram showing an example of a semiconductor integrated device in which the high-frequency band filter device according to the first embodiment of the present invention is integrated.
FIG. 7 is a diagram showing filter pass characteristics of the high-frequency band filter device according to the first embodiment of the present invention.
FIG. 8 is a block diagram showing a high-frequency band filter device according to a modification of the first embodiment of the present invention.
FIG. 9 is a block diagram showing a high-frequency band filter device according to a second embodiment of the present invention.
FIG. 10 is a diagram illustrating filter pass characteristics of a high-frequency band filter device according to a second embodiment of the present invention.
FIG. 11 is a block diagram showing a high-frequency band filter device according to a third embodiment of the present invention.
FIG. 12 is a sectional view showing an example of the switch circuit shown in FIG. 11;
FIG. 13 is a circuit diagram showing a conventional filter configuration.
FIG. 14 is a diagram showing a conventional filter characteristic.
[Explanation of symbols]
1. Portable information terminal
2. RF front end
3. Intermediate frequency processing unit
4: Baseband processing unit
5 Control terminal
6, 6a, 6b ... switch circuit
7 ... Antenna
8. Semiconductor package
11 to 14, 15 to 17: Piezoelectric thin film resonator type filter
21, 22, 23, 24 ... Low noise amplifier
25, 26, 27, 28 ... matching circuit
30, 30a, 30b, 30c ... Thin film type bulk acoustic wave resonator
31 ... Silicon substrate
32 ... buffer layer
33, 33a, 33b: Lower electrode
33c, 33d: Ground plate
34, 34a, 34b, 34c: Piezoelectric thin film
35a, 35b, 35c ... upper electrode
36a ... cavity (air gap)
37 ... First connection wiring
38 second connection wiring
41 ... ceramic substrate
51: High frequency band filter device
52 Local oscillator
53 ... Mixer
54 ... Amplifier
55 Automatic gain control (AGC) circuit
56… IF filter
57 ... I / Q demodulation circuit
58: IF local oscillator
60: Piezoelectric thin film actuator element
61 Silicon substrate
62 ... buffer layer
63 ... Lower electrode
64a: Piezoelectric thin film
66 ... cavity (air gap)
67a ... Switch electrode
71, 72, 73, 75, 76 ... antenna
81, 82 ... Baseband filter
83, 84 ... AD converter
85,86 ... Mixer
100, 101 ... filters
302 ... input side signal wiring
303 ... Output side signal wiring
411: Ground plate
501-506 ... Bump
521 ... resin
601 switch circuit chip
602: High frequency filter chip
603: Low noise amplifier chip
610: Ground plate

Claims (9)

A high-frequency filter device used in a specific communication band at 0.8 to 10 GHz,
A plurality of piezoelectric thin-film resonator type filters each having a different pass band from each other and selected so that the entire pass band covers the specific communication band, and arranged in parallel,
A high-frequency filter device comprising: a low-noise amplifier independently and directly connected to an output side of the piezoelectric thin-film resonator type filter. A switch circuit connected to an input side of each of the plurality of piezoelectric thin-film resonator-type filters, and selecting one of the plurality of piezoelectric thin-film resonator-type filters;
The high frequency band filter device according to claim 1, further comprising: an antenna for supplying a high frequency signal to the switch circuit. The high frequency band filter device according to claim 1, further comprising an antenna directly and independently connected to an input side of each of the plurality of piezoelectric thin film resonator type filters. The high-frequency band filter device according to any one of claims 1 to 3, further comprising a matching circuit independently and directly connected to an output side of the low noise amplifier. The high frequency band filter device according to any one of claims 1 to 4, wherein the piezoelectric thin film resonator type filter includes three thin film type elastic bulk acoustic wave resonators connected in a T-shape. The high frequency band filter device according to claim 5, wherein the thin film type elastic bulk acoustic wave resonator has a piezoelectric thin film having a thickness of 0.3 to 3 µm. The high frequency band filter device according to any one of claims 1 to 6, wherein the switch circuit is a semiconductor switch. The high frequency band filter device according to any one of claims 1 to 6, wherein the switch circuit is a piezoelectric thin film actuator element. A plurality of piezoelectric thin-film resonator-type filters whose passbands are selected to be different from each other, and a high-frequency front-end unit having a low-noise amplifier independently and directly connected to the output side of the piezoelectric thin-film resonator-type filter,
An intermediate frequency processing unit connected to the high frequency front end unit,
A baseband processing unit connected to the intermediate frequency processing unit,
A portable information terminal that performs communication in a specific communication band in a 0.8 to 10 GHz band.

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